Setting up remote digital DJ mixing station

[Michael Z Freeman]

Hi,

I have my decks across the room from my big Quad Core machine. Rather than relocating it which is a lot of hassle I'm using my Eee PC netbook as a "dumb" terminal to it over ethernet - the Eee Pc was unfortunately not quite fast enough for what I was wanting to do with realtime DJ'ing effects, My MIDI keyboard is also next to my decks ready to use as a MIDI controlled and play synths on my main machine (connected to it by a USB extension).

I almost have this working but have run into a few problems.

* Is it possible to run Mixxx with Jack Rack and have effects independently for each of the two channels in Mixxx ? Otherwise it's not possible to have, say, an echo on a vocal in the left channel and cross fade into the next track on the other without having echo over everything.

* Is Jack just extremely cantankerous ? I have a system board soundcard and a main Asus Xonar DX soundcard. I've had a few times when I've started Jack and not been able to get any sound. I found out today that something is flipping between the soundcards in the background. I'm pretty sure I did not hit anything myself. It seems to be something to do with ALSA and as you can imagine it get's very annoying .

* Vinyl control using a Serrato record. I only have a two channel mixer at the moment. Is there a way to get a signal out from the deck to Mixx and audio back to my mixer in some way, and keep it's functionality for playing vinyl ? Maybe using some kind of external splitter preamp or something ?

I am determined to setup this DJ'ing studio - this kind of setup is also closely connected with the way I make music using synths - but it's just like the film Gremlins at the moment

[autostatic]

* Is it possible to run Mixxx with Jack Rack and have effects independently for each of the two channels in Mixxx ? Otherwise it's not possible to have, say, an echo on a vocal in the left channel and cross fade into the next track on the other without having echo over everything.

This is not possible with the latest stable version (1.7.2) and neither with the upcoming 1.8.x version. But maybe there's something I've missed, I don't use Mixxx on a regular basis. And maybe it's possible to do a request or have someone take a look at the code, it shouldn't be too difficult to create two extra PortAudio outputs and assign the two pairs to the two decks.

* Is Jack just extremely cantankerous ? I have a system board soundcard and a main Asus Xonar DX soundcard. I've had a few times when I've started Jack and not been able to get any sound. I found out today that something is flipping between the soundcards in the background. I'm pretty sure I did not hit anything myself. It seems to be something to do with ALSA and as you can imagine it get's very annoying .

This is not a JACK issue, apparently your ALSA devices get assigned different hardware ID's every now and then. You can easily work around this by identifying your devices with aplay -l and using the ALSA names for the devices instead of their hardware ID's.

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aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: AD198x Analog [AD198x Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

So the card with ID 0 (hw:0 in ALSA terms) has a device name 'Intel' so it could also be addressed to as hw:Intel
If you do this consequently things never get mixed up, even if hardware ID's change. In the Setup window of QjackCtl the ALSA device names are not mentioned in the 'Interfaces' popup menu so you have to enter it manually.

[Michael Z Freeman]

Thanks so much . I had not grasped the part about hardware devices and ALSA. There is actually a little ">" next to the interfaces part in Jack that has a popup with the names (rather than ID's) of the devices which I ad failed to notice due to the stress of setting up all this new stuff.

I put in a blueprint for the jack channels - https://blueprints.launchpad.net/mixxx/ ... ach-player

I have this almost all working now with my netbook as the dumb terminal sitting between my decks .. ACE !

[autostatic]

I put in a blueprint for the jack channels - https://blueprints.launchpad.net/mixxx/ ... ach-player

Looks good

I have this almost all working now with my netbook as the dumb terminal sitting between my decks .. ACE !

Nice! Glad that I could help out a bit.

[Michael Z Freeman]

Hey, now have all this working apart from the Jack Rack effects. I can now crossfade between Mixxx players on my physical DJ mixer - with vinyl decks connected to it as well ! Analog and digital get it on together

The dual Jack channels can be setup using a simple trick as the docs put it. I have left the Blueprint in as Mixxx plans to have multiple software players that could be output to multiple Jack channels.

When I've used this for a while I will put together a guide about how I did all this. It is not easy to work out for the Jack novice and I've been using Computer and DJ setups for many years. Jack is very good but it could do with a little more intuition in the interface.

This is the culmination of a project that I've been pursuing for many years since about 98/99 when I realised that these multi channel surround sound cards could be used to provide the multiple digital outputs required for integrating with a mixer - hey, life happens as they say. I am using stereo Front and Side Surround outputs as inputs to my left and right channels on my two channel mixer - each channel can be flipped between vinyl and digital.

After yet ANOTHER hurdle (this is the audio Olympics, right?) I started using x11vnc to provide the remote control from my Asus EeePC netbook. Ubuntu Vino and Viangre although OK for most things actually cause the sound to stutter on my Quad Core PC.

Just bought a Steppenwolf album on vinyl as well from Oxfam to use in my new mix that is in development

[Michael Z Freeman]

Here it is ... see attachment.

I'll write this up if I get a chance but here are the basics.

> Be aware that Mixxx numbers channels from 1 whereas Portaudio-Jack numbers from 0.

> Mixxx sample rate must match Jack sample rate.

> The mouse pointer in the attachment image is pointing to the 'trick' that insures Mixxx players go to the right output channels to my physical DJ mixer. “Pre/Main” knob to the left (Mix knob on this skin). Cross fader to the left, as well as turning on the headphone cue for the right channel.

Follow the Jack connectors.

> Left Mixxx player goes (out 0 & 1) to left Jack Rack visible in the screenshot in the background.The left hand Jack Rack outputs are connected to the first channel of my multichannel (5.1 surround) soundcard, playback_1 and playback_2.

> Right Mixxx player ( out 6 & 7) goes to the right hand Jack Rack which is in turn connected to system playback 7 and 8 which is the other channel I am using for output from my soundcard to my physical mixer.

If this seems as clear as mud then you're not the only one ! Jack interface is innately confusing - at least to me it is - and the only way is to keep trying things until it makes sense. However it is worth it as this set up means a DJ can have access to the hundreds of effects available for Jack Rack on independent FX channels for each Mixxx player. Even on my physical two channel mixer this opens a nice amount of freedom. Once you get used to it you can swap around the Mixxx players so that being fixed to a particular physical output is not a restriction.

This is all being controlled from my mixing station using an Asus EeePC on my LAN.

Server on my audio workstation machine ...

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$> x11vnc -scale 0.7 -noxdamage

Viewer on the Eee...

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xtightvncviewer -fullscreen <LAN address>

That scales my 1440x900 screen quite nicely to the netbook.

So there it is. I hope this is all helpful to someone.